The about section of the linked page has links and a brief explanation of the story.

In my own words …

Description of the Turbo-fish syntax

• Whenever a generic type (see ch 10 of The Book) is involved in calling a function/method or constructing/handling a struct/enum, you may need to specify that concrete type for that generic.
  • See this handy blog post on the turbofish that lists when it’s necessary
• This type is provided with the turbo fish syntax: ::<> … where the type goes between the angle brackets.
• EG:

let v = Vec::new();

let v2 = Vec::<i32>::new()

• The elements of v have an undefined type, which rust will infer once an element is pushed into it. But v2 has a defined element type, i32, defined using the turbo fish.

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The Story

• This syntax wasn’t always liked, and the double colons (::) thought redundant.
• But it stuck
• And was given the name “turbo-fish” by Anna Harren (u/deadstone, Reddit) … who sadly passed away in 2021.
• It turns out that the double colons are pretty vital to preventing ambiguity.
• This is enshrined in the Bastion of the Turbofish which stands as a memorial to Anna Harren …
• a test in the language’s test suite that ensures that the double-colons syntax isn’t removed by directly using the ambiguous syntax that’d arise without it.
• See if you can understand the test (it took me a while! … this HN post might help):

let (the, guardian, stands, resolute) = ("the", "Turbofish", "remains", "undefeated");
let _: (bool, bool) = (the<guardian, stands>(resolute));

hint: what are angle brackets normally used for and how are bool types related to that?